The present disclosure is directed towards positioning instruments and related methods for implanting a joint unloading system, and more particularly to tools and surgical procedures for implanting a joint unloading system.
Joint replacement is one of the most common and successful operations in modern orthopaedic surgery. It consists of replacing painful, arthritic, worn or diseased parts of a joint with artificial surfaces shaped in such a way as to allow joint movement. Osteoarthritis is a common diagnosis leading to joint replacement. Such procedures are a last resort treatment as they are highly invasive and require substantial periods of recovery and permanently alter the joint. Total joint replacement, also known as total joint arthroplasty, is a procedure in which all articular surfaces at a joint are replaced. This contrasts with hemiarthroplasty (half arthroplasty) in which only one bone's articular surface at a joint is replaced and unincompartmental arthroplasty in which the articular surfaces of only one of multiple compartments at a joint (such as the surfaces of the thigh and shin bones on just the inner side or just the outer side at the knee) are replaced.
Arthroplasty as a general term, is an orthopaedic procedure which surgically alters the natural joint in some way. This includes procedures in which the arthritic or dysfunctional joint surface is replaced with something else, and procedures which are undertaken to reshape or realign the joint by osteotomy or some other procedure. As with joint replacement, these other arthroplasty procedures are also highly invasive procedures characterized by relatively long recovery times. A previously popular form of arthroplasty was interpositional arthroplasty in which the joint was surgically altered by insertion of some other tissue like skin, muscle or tendon within the articular space to keep inflammatory surfaces apart. Another previously done arthroplasty was excisional arthroplasty in which articular surfaces were removed leaving scar tissue to fill in the gap. Among other types of arthroplasty are resection(al) arthroplasty, resurfacing arthroplasty, mold arthroplasty, cup arthroplasty, silicone replacement arthroplasty, and osteotomy to affect joint alignment or restore or modify joint congruity. When successful, arthroplasty results in new joint surfaces which serve the same function in the joint as did the surfaces that were removed. Any chondrocytes (cells that control the creation and maintenance of articular joint surfaces), however, are either removed as part of the arthroplasty, or left to contend with the resulting joint anatomy. Because of this, none of the therapies which remove the joint surfaces are chondro-protective.
A widely-applied type of osteotomy is one in which bones are surgically cut to improve alignment. A misalignment due to injury, bone abnormality or disease in a joint relative to the direction of load can result in an imbalance of forces and pain in the affected joint. The goal of osteotomy is to surgically re-align the bones at a joint and thereby relieve pain by shifting forces across the joint to less damaged joint surfaces. This can also increase the lifespan of the joint. When addressing osteoarthritis in the knee joint, this procedure involves surgical re-alignment of the joint by cutting and reattaching part of one of the bones at the knee to change the joint alignment, and this procedure is often used in younger, more active or heavier patients. Most often, high tibial osteotomy (HTO) (the surgical re-alignment of the upper end of the shin bone (tibia) to address knee malalignment) is the osteotomy procedure done to address osteoarthritis and it often results in a decrease in pain and improved function. However, HTO does not address ligamentous instability—only mechanical alignment. HTO is associated with good early results, but results deteriorate over time.
It has been found that excess loading of the joint is the primary contributing factor in the progression of osteoarthritis disease. It has also been shown that a decrease in load, such as by weight loss can result in decrease in disease progression and in pain relief.
Certain approaches to treating osteoarthritis contemplate external devices such as braces or fixators which attempt to control the motion of the bones at a joint or apply cross-loads at a joint to shift load from one side of the joint to the other. A number of these approaches have had some success in alleviating pain by reducing loads on diseased joints but have ultimately been unsuccessful due to lack of patient compliance or the inability of the devices to facilitate and support the natural motion and function of the diseased joint.
Certain prior approaches to treating osteoarthritis have also failed to account for all of the basic functions of the various structures of a joint in combination with its unique movement. In addition to addressing the loads and motions at a joint, an ultimately successful approach should both acknowledge the dampening and energy absorption functions of the anatomy, and be implantable via a minimally invasive technique. Device constructs which are relatively rigid do not allow substantial energy storage. For these relatively rigid constructs, energy is transferred rather than stored or absorbed relative to a joint. By contrast, the natural joint is a construct comprised of elements of different compliance characteristics such as bone, cartilage, synovial fluid, muscles, tendons, ligaments, etc. as described above. These dynamic elements include relatively compliant ones (ligaments, tendons, fluid, cartilage) which allow for substantial energy absorption and storage, and relatively stiffer ones (bone) that allow for efficient energy transfer. The cartilage in a joint compresses under applied force and the resultant force displacement product represents the energy absorbed by cartilage. The fluid content of cartilage also acts to stiffen its response to load applied quickly and dampen its response to loads applied slowly. In this way, cartilage acts to absorb and store, as well as to dissipate energy.
Approaches for surgically implanting extra-articular mechanical joint unloading apparatus or joint unloading systems have been developed. As precise and effective placement are important to the efficacy of an implanted extra-articular mechanical unloading apparatus, further advancements in patient preparation and device-to-anatomy juxapositional relationships have been found to be both useful and necessary.
With the foregoing applications in mind, it has been found to be necessary to develop effective systems and tools for mounting implantable joint unloading system to body anatomy.
For joint unloading systems to function optimally, they must be selected and positioned to unload the joint without overloading the implant. Therefore, what is needed is a refined surgical approach to implanting a device which complements underlying or adjacent anatomy. The present disclosure satisfies these and other needs.